Generally described, gas turbine buckets often include an airfoil with an integral tip shroud attached thereto. The tip shroud attaches to the outer edge of the airfoil and provides a surface that runs substantially perpendicular to the airfoil surface. The surface area of the tip shroud helps to hold the turbine exhaust gases on the airfoil such that a greater percentage of the energy from the turbine exhaust gases may be converted into mechanical energy so as to increase overall turbine efficiency. The tip shroud also provides aeromechanical damping and shingling (fretting) prevention to the airfoil.
A seal rail may be used on the tip shroud as a sealing feature with respect to the hot gases flowing thereover. The seal rail may be attached to the shroud with a fillet and may terminate at a Z-notch intersection on one or both ends. The relatively high temperature environment and the bending stresses caused by the overhanging material and centrifugal loading on the tip shroud, however, may drive creep (deformation) therein. Specifically, these bending stresses and the like may cause localized high stress concentrations in the Z-notch intersections and elsewhere. Using a larger fillet to attach the seal rail may help reduce such Z-notch stresses but at the cost of increasing the overhung mass of the shroud.
There is thus a desire for an improved tip shroud assembly. Such an improved tip shroud assembly may use an expanded fillet to attach the seal rail to the shroud so as to reduce the stresses at the Z-notches and elsewhere, but while adding only a small amount of additional mass so as to improve the overall lifespan of the bucket and the components thereof.